Conventional acoustic ceiling tile is a non-woven structure which may include a core composed of base fibers, fillers, and binders combined to form the ceiling tile structure. The base fibers can be natural or synthetic materials, e.g., mineral fibers. Typically mineral fiber substrates of acoustical ceiling panels are wet-formed and fall within the density range of 9-25 lb/ft3. Their porosities range low from 50-89% and therefore sound absorption is lower with NRCs ranging 0.50-0.75 after finishing and decorating the surfaces. They are usually wet-formed, bound with starch, and require large amounts of energy to remove residual water from the forming process. Surfaces must then be sanded smooth and material is wasted.
There are existing dry-formed mineral fiber and fiber glass acoustical ceiling products in which the web is in the density range of the invention; however these webs are poorly formed with irregular formation and require expensive face scrims and back scrims to impart adequate product surface quality and sufficient rigidity for the panel to be self-supporting in the ceiling grid. Most often such webs are bound with a phenolic resin that emits formaldehyde in the manufacturing process and some residual from the product. Other non-formaldehyde reactive resins, i.e. acrylic acid esters, are beginning to be used as well, but they require excess heat to drive off solution water and to drive the reaction. They are difficult to apply and often complicate the web forming process.
Thus, there remains a need for highly acoustically absorptive ceiling tiles with sufficient rigidity and acceptable surface quality, which can be easily cut or molded into complex shapes or embossed with surface patterns; and also avoid the challenges provided by the use of certain binding resins. Embodiments of the present invention are directed to this and other ends.